Chiggers seek out and climb to the top of grass/weeds where they are in the ideal position to crawl onto anything that brushes by. So one of the best defenses is to keep grass and weeds mowed down. They don't seem to be able to figure out what to do in a large mowed or bushhogged area since nothing is "tall". We have tons of chiggers in central TN, but in areas that we frequent we just keep the weeds down and there is almost no problem from chiggers in these areas.
Once on you, they crawl to "edges" (pants cuffs, top of socks, waistbands, collarbands, etc.) where they can get on fresh skin. They'll usually crawl down past the "edge" to where it is dark, hot, moist, and they have "cover" to push against. Permanone works great on exterior clothing and boots to prevent them from crawling around to find an edge. We always spray down boots really well in the spring, and maybe one repeat application mid-summer. It lasts a long time when soaked into leather. Don't use Permanone on skin, use DEET. DEET sprays will cause them to either die or just drop off (I don't care which). We use the "heavy" 40% or more stuff. If you are only going in grassy/weedy areas, a good coating around ankles, spread up to the knees is usually sufficient. MAKE SURE to pull down those socks and coat under them good. If you don't, they'll get to the top of the sock edge and then go down inside. This is how all the ankle bites happen! Make sure to have a good solid coat all around the knees, particularly the BACK where pants provide good "cover". This will also minimize chances that they crawl UP your legs to much more sensitive itch spots! If you'll be out in forested areas or where there's HIGH weeds (blackberry vines!!) you'll also need to go around your neckline, waistband, armbands. This will prevent the majority of bites.
They do NOT burrow into/under your skin as most folks believe. They DO inject saliva with really nasty enzymes that essentially dissolve your flesh and then they slurp up the goo. Somewhat similar to brown recluse spiders, but not quite that bad. It is the resulting dissolved flesh wound that itches so bad and takes so long to heal.
Showering thoroughly as soon as practical after being in a known exposure area is helpful, but I really don't understand why, since their damage (it seems to me) is usually done within at most an hour or so. Wash particularly well in those dark, hot, moist areas where there has been pressure from clothing!
Hope this saves ya at least a few bites!